Use of tyrosine kinase inhibitors to prevent relapse after allogeneic hematopoietic stem cell transplantation for patients with Philadelphia chromosome-positive acute lymphoblastic leukemia: A position statement of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Philadelphia-chromosome positive acute lymphoblastic leukemia: ten frequently asked questions

Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) constitutes a distinctive cytogenetic entity associated with challenging outcomes, particularly in adult patients. Current upfront chemotherapy-tyrosine kinase inhibitor (TKI)-based therapies include first, second and third-generation TKIs that have revolutionized patient outcomes including molecular remission and overall survival. Chemotherapy-free regimens such as blinatumomab-dasatinib or blinatumomab-ponatinib offer exciting possibilities, yet challenges arise, particularly in preventing central nervous system relapse. Monitoring measurable residual disease is now a cornerstone particularly using next-generation sequencing (NGS)-Clonoseq for accurate assessment. Controversy regarding the ability to omit consolidation with allogeneic stem cell transplantation, specifically for patients achieving early molecular remission, is related to the excellent survival achieved with novel combinations in the upfront setting, however challenged by the lower disease control when transplant is utilized beyond first remission. Post-transplant maintenance introduces new dilemmas: the optimal TKI, dosing, and duration of therapy are open questions. Meanwhile, a myriad of new combinations and cellular therapies are used for relapsed Ph+ ALL, prompting us to unravel the optimal sequencing of these promising regimen. In this review, we delve into the breakthroughs and controversies in Ph+ ALL with ten commonly asked questions.

Comparison of long-term outcomes between imatinib and dasatinib prophylaxis after allogeneic stem cell transplantation in patients with Philadelphia-positive acute lymphoblastic leukemia: A multicenter retrospective study

BACKGROUND

Although the prognosis of Philadelphia-positive acute lymphoblastic leukemia (Ph+ ALL) has improved with the introduction of tyrosine kinase inhibitors (TKIs) and stem cell transplantation, prevention of relapse after transplantation remains a concern. The aim of this study was to compare the impact of TKI prophylaxis with imatinib and dasatinib on long-term outcomes after transplantation.

METHODS

Patients with Ph+ ALL who underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) at first complete remission (CR1) and received TKI prophylaxis after allo-HSCT were included in this retrospective analysis. Two cohorts were established based on the choice of TKI prophylaxis: the imatinib (Ima) and dasatinib (Das) cohorts. The survival and safety outcomes of these cohorts were compared.

RESULTS

Ninety-one patients in the Ima cohort and 50 in the Das cohort were included. After a median follow-up of 50.6 months, the 5-year cumulative incidence of relapse, nonrelapse mortality rate, and overall survival in the Ima and Das cohorts were 16.1% and 12.5%, 5.2% and 9.8%, and 86.5% and 77.6%, respectively, with no statistical differences. The cumulative incidence of mild chronic graft-versus-host disease was higher in the Das cohort. The most common adverse event was neutropenia (64.7% vs. 69.5%). The Das cohort had a higher incidence of gastrointestinal bleeding (25.5% vs. 2.3%) and gastrointestinal reaction (48.9% vs. 31.4%) than the Ima cohort. The proportion of patients treated on schedule was significantly lower in the Das cohort than in the Ima cohort, and drug intolerance was the main reason for protocol violation.

CONCLUSIONS

For patients with Ph+ ALL undergoing allo-HSCT in CR1, imatinib prophylaxis achieved long-term outcomes similar to those of dasatinib.

Ponatinib as a Prophylactic or Pre-Emptive Strategy to Prevent Cytological Relapse after Allogeneic Stem Cell Transplantation in Patients with Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia Transplanted in Complete Cytological Remission

The administration of TKIs after Allo-SCT in Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph + ALL) remains controversial, and the TKI approach (prophylactic, pre-emptive or salvage) is still heterogeneous in transplant centers. In this context, very little is known about the feasibility and safety of third-generation TKIs. In this paper, we analyze the efficacy and safety of ponatinib (PONA) administered after Allo-SCT to prevent cytologic relapse of Ph + ALL. This is a multicenter observational study including 48 patients (pts) with Ph + ALL (median age 49 years) who received PONA after Allo-SCT while in complete cytological remission (cCR); 26 (54%) had positive minimal residual disease (MRD pos) before Allo-SCT. PONA was administered after Allo-SCT prophylactically (starting with MRD neg) in 26 pts or pre-emptively (starting with MRD pos post-SCT and without hematological relapse) in 22 pts. Patients treated prophylactically with PONA started treatment earlier, at a median of 4.3 months (range 1.5-6) after Allo-SCT, than those treated pre-emptively, who started PONA at a median of 7.4 months (range 2-63) after Allo-SCT (p = 0.01). The median starting dose of PONA was 30 mg/day (range 15-45). A dose reduction was required in 10/48 (21%) of cases, but a permanent discontinuation of PONA, due to toxicity, was required in only 5/48 pts (10.5%). No deaths due to PONA-related adverse events (AEs) were reported. The median follow-up time after Allo-SCT was 34 months (range 7.7-118). At the last follow-up, the median duration of PONA therapy was 22 months (range 2-100). The 5-year OS and RFS after Allo-SCT were 92% and 71%, respectively. The 5-year RFS after Allo-SCT of pts who received PONA prophylaxis was 95%, and it was 57% for those who received PONA pre-emptively (log-rank p = 0.02). In conclusion, this multicenter analysis of 48 patients with Ph + ALL undergoing Allo-SCT while in CcR, although with the caution of the retrospective data, supports the feasibility of PONA maintenance strategy after Allo-SCT with a low rate of discontinuations (10.5%) due to PONA-related AE.

Toxicities associated with tyrosine kinase inhibitor maintenance following allogeneic hematopoietic cell transplantation in Philadelphia chromosome-positive acute lymphoblastic leukemia

Allogeneic hematopoietic cell transplantation (HCT) offers a potential cure in Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL); nonetheless, relapses are common and the major cause of mortality. One strategy to prevent relapse is tyrosine kinase inhibitor (TKI) maintenance post-HCT, but published clinical experience is primarily with the first-generation TKI imatinib while data with newer generation TKIs are limited. We conducted a retrospective analysis of 185 Ph+ ALL patients who underwent HCT followed by TKI maintenance from 2003 to 2021 at City of Hope. Initially, 50 (27.0%) received imatinib, 118 (63.8%) received a second-generation TKI (2G-TKI), and 17 (9.2%) received ponatinib. A total of 77 patients (41.6%) required a dose reduction of their initial TKI due to toxicity. Sixty-six patients (35.7%) did not complete maintenance due to toxicity; 69 patients (37.3%) discontinued 1 TKI, and 11 (5.9%) discontinued 2 TKIs due to toxicity. Initial imatinib versus 2G-TKI versus ponatinib maintenance was discontinued in 19 (38.0%) versus 68 (57.6%) versus 3 (17.6%) patients due to toxicity (p = .003), respectively. Patients on ponatinib as their initial TKI had a longer duration of TKI maintenance versus 2G-TKI: 576.0 days (range, 72-921) versus 254.5 days (range, 3-2740; p = .02). The most common reasons for initial TKI discontinuation include gastrointestinal (GI) intolerance (15.1%), cytopenia (8.6%), and fluid retention (3.8%). The 5-year overall survival and progression-free survival for the total population were 78% and 71%, respectively. Our findings demonstrate the challenges of delivering post-HCT TKI maintenance in a large real-world cohort as toxicities leading to TKI interruptions, discontinuation, and dose reduction were common.

Management of ALL in adults: 2024 ELN recommendations from a European expert panel

ABSTRACT

Experts from the European Leukemia Net (ELN) working group for adult acute lymphoblastic leukemia have identified an unmet need for guidance regarding management of adult acute lymphoblastic leukemia (ALL) from diagnosis to aftercare. The group has previously summarized their recommendations regarding diagnostic approaches, prognostic factors, and assessment of ALL. The current recommendation summarizes clinical management. It covers treatment approaches, including the use of new immunotherapies, application of minimal residual disease for treatment decisions, management of specific subgroups, and challenging treatment situations as well as late effects and supportive care. The recommendation provides guidance for physicians caring for adult patients with ALL which has to be complemented by regional expertise preferably provided by national academic study groups.

How I treat newly diagnosed acute lymphoblastic leukemia

Treatment algorithms differ for adult patients with Philadelphia-negative (Ph-) and Philadelphia-positive (Ph+) acute lymphoblastic leukemia (ALL). For Ph- ALL intensive induction-consolidation chemotherapy using "pediatric-inspired" protocols is a standard of care. Allogeneic hematopoietic cell transplantation (allo-HCT) from either an HLA-matched sibling, unrelated or haploidentical donor should be considered for patients with high estimated risk of relapse. Inadequate response at the level of measurable residual disease (MRD) is the strongest adverse prognostic factor. Patients with B-ALL and detectable MRD should be treated with blinatumomab. In the future, the use of blinatumomab and/or inotuzumab ozogamycin in addition to first-line chemotherapy may become a new standard of care reducing the role of allo-HCT. For patients with Ph+ ALL, tyrosine kinase inhibitors (TKI) are the most important components of treatment protocols, while the intensity of chemotherapy may be reduced. Allo-HCT is recommended for all patients treated with imatinib along with low-intensity chemotherapy. Results of phase-II studies using front-line dasatinib or ponatinib in sequence or in combination with blinatumomab are very promising. Such a strategy may allow the avoidance of systemic chemotherapy. The future role of allo-HCT in this context appears uncertain.

SOHO State of the Art Updates and Next Questions: Update on the Approach to Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia

The outcome of Philadelphia chromosome (Ph)-positive acute lymphoblastic leukemia (ALL) has improved significantly following the introduction of the BCR::ABL1 tyrosine kinase inhibitors (TKIs). The addition of newer-generation and more potent TKIs resulted in higher rates of molecular responses and better survival. Achieving a complete molecular remission (CMR; disappearance of the BCR::ABL1 transcripts) within the first 3 months of therapy is an important endpoint in newly diagnosed Ph-positive ALL that identifies patients who have an excellent long-term survival and who may not need to receive an allogeneic hematopoietic stem cell transplantation (HSCT) in first complete remission (CR). Chemotherapy-free combinations with blinatumomab plus TKIs showed encouraging results with estimated 2 to 4 year overall survival (OS) rates of 80% to 90%. Treatment with blinatumomab and ponatinib resulted in a CMR rate of 84%, a 2-year event-free survival (EFS) of 78%, and a 2-year OS rate of 90%; only 1 patient underwent HSCT. The detection of measurable residual disease (MRD) is the most important factor predicting for disease relapse. Studies have shown that the next-generation sequencing (NGS) assay is more sensitive than RT-PCR for the detection of MRD in Ph-positive ALL. Approximately 15% to 30% of patients who achieve NGS MRD negativity at a sensitivity of 1 × 10-6 may still have detectable BCR::ABL1 transcripts by RT-PCR. Achieving NGS MRD negativity can also identify patients who may have durable remissions with a low risk of relapse. Herein, we discuss the current approach to the management of adults with Ph-positive ALL, the role of HSCT, MRD monitoring, and future therapies.

Reduced-intensity allogenic transplantation for children and adolescents with Philadelphia chromosome-positive acute lymphoblastic leukemia

Survival rates of patients with Philadelphia chromosome-positive ALL (Ph+ALL) have improved considerably with the introduction of tyrosine kinase inhibitors (TKI); however, hematopoietic stem cell transplantation (HSCT) continues to play an important role. Reduced-intensity conditioning (RIC) regimens have been widely applied particularly for older patients, but their validity for children and adolescents with Ph+ALL has not been investigated. In this study, data from patients receiving HSCT for de novo Ph+ALL in first or second remission at ages younger than 25 years and with a history of pre-HSCT TKI therapy were retrospectively collected through the nationwide registry in Japan. In 265 patients who received myeloablative conditioning (MAC) and 33 patients receiving RIC, 5-year leukemia-free survival (LFS) rates were 67.3% and 79.8%, respectively (p = 0.142). Multivariate analysis of LFS, focusing on patients with good performance status, identified RIC as a significant prognostic factor for LFS (hazard ratio 0.32, p = 0.032), as well as older age, higher leukocyte count at diagnosis, and disease with additional chromosomal abnormalities. These trends were similar when we focused on patients who received prophylactic post-HSCT TKI treatment, as 5-year LFS was 81.0% for MAC and 84.4% for RIC (p = 0.748). In summary, HSCT with RIC regimen showed at least comparable LFS to HSCT with MAC regimen, and RIC was an independent favorable prognostic factor on multivariate analysis adjusting potential prognostic factors. While patient numbers were limited, our data suggest that RIC may be safely applied in this group, particularly combined with prophylactic post-HSCT TKI maintenance therapy.

Biological Markers of High-Risk Childhood Acute Lymphoblastic Leukemia

Childhood acute lymphoblastic leukemia (ALL) has witnessed substantial improvements in prognosis; however, a subset of patients classified as high-risk continues to face higher rates of relapse and increased mortality. While the National Cancer Institute (NCI) criteria have traditionally guided risk stratification based on initial clinical information, recent advances highlight the pivotal role of biological markers in shaping the prognosis of childhood ALL. This review delves into the emerging understanding of high-risk childhood ALL, focusing on molecular, cytogenetic, and immunophenotypic markers. These markers not only contribute to unraveling the underlying mechanisms of the disease, but also shed light on specific clinical patterns that dictate prognosis. The paradigm shift in treatment strategies, exemplified by the success of tyrosine kinase inhibitors in Philadelphia chromosome-positive leukemia, underscores the importance of recognizing and targeting precise risk factors. Through a comprehensive exploration of high-risk childhood ALL characteristics, this review aims to enhance our comprehension of the disease, offering insights into its molecular landscape and clinical intricacies in the hope of contributing to future targeted and tailored therapies.

Myeloablative or reduced-intensity/non-myeloablative hematopoietic cell transplantation for Philadelphia-positive acute lymphoblastic leukemia in adults older than 40 years old - a secondary analysis of a CIBMTR database

Few studies have addressed the role of reduced-intensity conditioning (RIC) and non-myeloablative (NMA) regimens in older adults with Philadelphia acute lymphoblastic leukemia (Ph + ALL). The objective of this current study was to compare the outcomes of RIC/NMA versus TBI-based myeloablative (MAC) regimens in Ph + ALL patients older than 40 years old who underwent hematopoietic cell transplantation (HCT) in CR1. We used a freely available database from the CIBMTR. Transplants were performed between 2013 and 2017. With a median follow-up of 37.6 months, we have included 629 patients. We used propensity score weighting. Three-year OSs were 64% in the TBI-MAC group and 66% in the RIC/NMA group. OS was not different (HR = 0.92; p = 0.69). Three-year relapse incidences were 21.6% and 27.6% in the TBI-MAC and RIC/NMA groups. RIC/NMA was not associated with an increase in relapse rate (HR 1.02; p = 0.91). Three-year NRMs were 24.3% in the TBI-MAC group and 20.3% in the RIC/NMA group. RIC/NMA was not associated with superior NRM (HR 0.88; p = 0.57). In summary, we have shown that RIC/NMA regimens achieve outcomes comparable to TBI-based MAC in Ph+ ALL older patients in CR1 who may tolerate a TBI-based MAC regimen.

Global burden of leukemia attributable to occupational exposure to formaldehyde from 1990 to 2019

The objective of this study was to evaluate the worldwide burden of leukemia owing to occupational exposure to formaldehyde (OEF) from 1990 to 2019. Data on leukemia due to OEF were obtained from the Global Burden of Disease Study (GBD) 2019. By region, age, sex, and disease subtype, the numbers and age-standardized rates (ASRs) associated with deaths, years of life lost (YLLs), years lived with disability (YLDs), and disability-adjusted life years (DALYs) were analyzed. Annual average percentage change (AAPC) was used to estimate disease burden trends from 1990 to 2019. To measure the risk of leukemia due to OEF, the population attributable fraction (PAF) was introduced. From 1990 to 2019, the number of deaths, DALYs, YLLs, and YLDs for leukemia caused by OEF increased by 44%, 34%, 33%, and 124%, respectively. Regarding the change in ASRs, the age-standardized YLDs (ASYLDs) rate of leukemia due to OEF, which was 38.03% (AAPC = 1.17 [95% confidence interval [CI] 1.11, 1.23]), indicated an increased trend. But the age-standardized mortality rate (ASMR), age-standardized DALY (ASDALY) rate, and age-standardized YLL (ASYLL) rate showed decline trends, with - 11.90% (AAPC =  - 0.41 [95% CI - 0.45, - 0.37]), - 14.19% (AAPC =  - 0.5 [95% CI - 0.55, - 0.45]), and - 14.97% (AAPC =  - 0.53 [95% CI - 0.58, - 0.48]), respectively. In terms of PAFs, there were increasing trends in PAFs of age-standardized deaths, ASDALYs, ASYLLs, and ASYLDs for leukemia caused by OEF, with 20.15% (95% uncertainty interval [UI] 11.76%, 30.25%), 36.28% (95% UI 21.46%, 53.42%), 51.91% (95% UI 35.05%, 72.07%), and 36.34% (95% UI 21.58%, 53.63%), respectively. Across the socio-demographic index (SDI) regions, the leukemia burden caused by OEF was concentrated in middle and high-middle SDI regions. Besides, OEF poses a more serious risk for acute leukemia among the leukemia subtype. Globally, leukemia caused by OEF remains a public health burden. Policies must be developed to avoid the burden of leukemia caused by OEF.

Prophylactic versus Preemptive modified donor lymphocyte infusion for high-risk acute leukemia after allogeneic hematopoietic stem cell transplantation: a multicenter retrospective study

Donor lymphocyte infusion (DLI) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been widely used in preventing post-transplant relapse. We conducted this study to compare the superiority of prophylactic modified DLI (pro-DLI) and preemptive modified DLI (pre-DLI) in patients with high-risk relapse features acute leukemia. Pro-DLI was performed in 95 patients, whereas the pre-DLI cohort included 176 patients. In the pre-DLI cohort, 42 patients relapsed without chance for pre-DLI while 95 patients remained CR without detectable minimal residual disease (MRD). Thirty-nine patients in the pre-DLI cohort became minimal MRD positive/mixed chimerism and received pre-DLI. Pro-DLI cohort had higher 3-year progression-free-survival (PFS) (63.4%vs.53.0%, P = 0.026) and overall survival (OS) (65.2% vs. 57.0%, P = 0.14) compared to the pre-DLI cohort. The 3-year cumulative incidence of relapse (CIR) was 25.3% in the pro-DLI cohort which was significantly lower than 36.7% in the pre-DLI cohort (P = 0.02). The cumulative incidence of grade III-IV aGVHD, cGVHD and non-relapse mortality were comparable between cohorts. Multivariable analysis demonstrated strong protective effect of pro-DLI on OS (hazard ratio (HR) = 0.63, P = 0.04), PFS (HR = 0.54, P = 0.005) and CIR (HR = 0.50, P = 0.005). In high-risk patients with acute leukemia, early scheduled pro-DLI rather than pre-DLI after detectable MRD would reduce post-transplant relapse and improve long-term survival.

How to Manage Philadelphia-Positive Acute Lymphoblastic Leukemia in Resource-Constrained Settings

Recent studies have indicated that more than half of adult patients newly diagnosed with Ph+ ALL can now achieve a cure. However, determining the most suitable protocol for less-resourced settings can be challenging. In these situations, we must consider the potential for treatment toxicity and limited access to newer agents and alloSCT facilities. Currently, it is advisable to use less intensive induction regimens for Ph+ ALL. These regimens can achieve high rates of complete remission while causing fewer induction deaths. For consolidation therapy, chemotherapy should remain relatively intensive, with careful monitoring of the BCR-ABL1 molecular transcript and minimal residual disease. AlloSCT may be considered, especially for patients who do not achieve complete molecular remission or have high-risk genetic abnormalities, such as IKZF1-plus. If there is a loss of molecular response, it is essential to screen patients for ABL mutations and, ideally, change the TKI therapy. The T315I mutation is the most common mechanism for disease resistance, being targetable to ponatinib. Blinatumomab, a bispecific antibody, has shown significant synergy with TKIs in treating this disease. It serves as an excellent salvage therapy, aside from achieving outstanding results when incorporated into the frontline.

Ponatinib Improved the Prognosis of Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia: A Japanese Single-Center Cohort Study

Introduction The overall survival (OS) of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL) has improved with the combination of tyrosine kinase inhibitor (TKI) with intensive chemotherapy. In recent years, there has been increased interest in the possibility of long-term survival without allogeneic hematopoietic stem cell transplantation (HSCT) or maintenance therapy. The aim of this study was to determine the effectiveness of treatment and the resultant outcomes in Ph+ALL patients using real-world data. Methods We performed a single-center retrospective analysis utilizing Akita University Hospital data (Akita, Japan) from November 2000 to June 2023 to evaluate the outcomes of TKI with intensive chemotherapy for Ph+ALL. Results Twenty-three patients with Ph+ALL were treated with intensive chemotherapy combined with TKI, including six imatinib, four dasatinib, and 13 ponatinib. The median patient age was 53 years (range; 28-67). Eighteen patients (78%) achieved complete molecular remission (CMR) within three months. HSCT was performed in 16 patients (70%), all of whom did not receive post-transplant TKI maintenance therapy. Six of the seven patients who did not undergo HSCT received maintenance therapy with ponatinib after intensive chemotherapy. The three-year OS was 81%. Ponatinib treatment resulted in a much higher OS rate than imatinib/dasatinib (100% vs. 60%; P=0.011). CMR within three months was identified as a prognostic factor for molecular relapse-free survival (hazard ratio (HR)=0.22; P=0.027). CD20 positivity was identified as a risk factor for hematological relapse (HR=5.2, P=0.032). Conclusion Even in a single-center cohort study, ponatinib, as a combination TKI with intensive chemotherapy or maintenance therapy, may improve the prognosis of Ph+ALL. Patients with CMR within three months might not necessarily need to receive HSCT, but a subsequent treatment-free status could have been achieved only by HSCT. Furthermore, CD20 positivity may be a useful biomarker for future treatment decisions in patients with Ph+ALL.

SOHO State of the Art Updates and Next Questions | Philadelphia Chromosome Positive Acute Lymphoblastic Leukemia in Adults: Therapeutic Options and Challenges in 2023

The therapeutic landscape of Philadelphia chromosome positive acute lymphoblastic leukemia (ALL) for adults has dramatically changed over the past 2 decades; the emergence of newer generations of tyrosine kinase inhibitors and incorporation of targeted immunotherapies into front-line therapy have significantly improved outcomes to the point where an argument can be made that this entity may no longer be considered a high-risk ALL subgroup. In this review article, we discuss different front-line regimens (both intensive and deintensified regimens including chemotherapy-free regimens). We also review disease monitoring strategies, discuss the role of allogeneic hematopoietic stem cell transplantation, and discuss the rapidly changing therapeutic landscape for patients with relapsed disease.

A pilot study of implication of machine learning for relapse prediction after allogeneic stem cell transplantation in adults with Ph-positive acute lymphoblastic leukemia

The posttransplant relapse in Ph-positive ALL increases the risk of death. There is an unmet need for instruments to predict the risk of relapse and plan prophylaxis. In this study, we analyzed posttransplant data by machine learning algorithms. Seventy-four Ph-positive ALL patients with a median age of 30 (range 18-55) years who previously underwent allo-HSCT, were retrospectively enrolled. Ninety-three percent of patients received prophylactic/preemptive TKIs after allo-HSCT. The values of the BCR::ABL1 level at serial assessments and over variables were collected in specified intervals after allo-HSCT. They were used to model relapse risk with several machine-learning approaches. GBM proved superior to the other algorithms and provided a maximal AUC score of 0.91. BCR::ABL1 level before and after allo-HSCT, prediction moment, and chronic GvHD had the highest value in the model. It was shown that after Day + 100, both error rates do not exceed 22%, while before D + 100, the model fails to make accurate predictions. As a result, we determined BCR::ABL1 levels at which the relapse risk remains low. Thus, the current BCR::ABL1 level less than 0.06% in patients with chronic GvHD predicts low risk of relapse. At the same time, patients without chronic GVHD after allo-HSCT should be classified as high risk with any level of BCR::ABL1. GBM model with posttransplant laboratory values of BCR::ABL1 provides a high prediction of relapse after allo-HSCT in the era of TKIs prophylaxis. Validation of this approach is warranted.

Total body irradiation versus busulfan based intermediate intensity conditioning for stem cell transplantation in ALL patients >45 years-a registry-based study by the Acute Leukemia Working Party of the EBMT

Allogeneic hematopoietic cell transplantation is a potentially curative treatment in high-risk acute lymphoblastic leukemia (ALL). Conditioning regimens based on ≥12 Gray total body irradiation (TBI) represent the current standard in patients ≤45 years, whereas elderly patients frequently receive intermediate intensity conditioning (IIC) to reduce toxicity. To evaluate the role of TBI as a backbone of IIC in ALL, a retrospective, registry-based study included patients >45 years transplanted from matched donors in first complete remission, who had received either fludarabine/TBI 8 Gy (FluTBI8, n = 262), or the most popular, irradiation-free alternative fludarabine/busulfan, comprising busulfan 6.4 mg/kg (FluBu6.4, n = 188) or 9.6 mg/kg (FluBu9.6, n = 51). At two years, overall survival (OS) was 68.5%, 57%, and 62.2%, leukemia-free survival (LFS) was 58%, 42.7%, and 45%, relapse incidence (RI) was 27.2%, 40%, and 30.9%, and non-relapse-mortality (NRM) was 23.1%, 20.7%, and 26.8% for patients receiving FluTBI8Gy, FluBu6.4, and FluBu9.6, respectively. In multivariate analysis, the risk of NRM, acute and chronic graft-versus-host disease was not influenced by conditioning. However, RI was higher after FluBu6.4 (hazard ratio [HR] [95% CI]: 1.85 [1.16-2.95]), and LFS was lower after both FluBu6.4 (HR: 1.56 [1.09-2.23]) and FluBu9.6 (HR: 1.63 [1.02-2.58]) as compared to FluTBI8. Although only resulting in a non-significant advantage in OS, this observation indicates a stronger anti-leukemic efficacy of TBI-based intermediate intensity conditioning.

Novel strategies to prevent and overcome relapse after allogeneic hematopoietic cell transplantation in acute lymphoblastic leukemia

The outcome of B-cell acute lymphoblastic leukemia (B-ALL) has improved over time with the incorporation of multi-agent chemotherapy in the treatment landscape as well as the recent approval of immunotherapeutic agents allowing a larger proportion of patients to undergo allogeneic hematopoietic cell transplantation (allo-HCT) which is still considered a potential curative approach. However, relapse post-transplant is still occurring and constitutes a common cause of treatment failure in B-ALL. The present review aims to discuss the novel strategies and therapies used to prevent and overcome relapse post allo-HCT in patients with ALL, focusing on the role of tyrosine kinase inhibitors in Philadelphia chromosome positive B-ALL, the role of innovative agents such as blinatumomab and inotuzumab ozogamicin, and finally the role of cellular therapy.

Outcomes of allogeneic or autologous stem cell transplantation followed by maintenance chemotherapy in adult patient with B-ALL in CR1 with no detectable minimal residual disease

Autologous haematopoietic stem cell transplantation (auto-HSCT) as a treatment for B-cell acute lymphoblastic leukaemia (B-ALL) has been rigorously debated in recent years. We retrospectively analysed the outcomes of 355 adult patients with B-ALL in first complete remission who had received auto-HSCT or allogeneic HSCT (allo-HSCT) in our centre. The treatment efficacy was evaluated from a model stratified on the risk classification and minimal residue disease (MRD) status after three chemotherapy cycles. Auto-HSCT demonstrated comparable 3-year overall survival (OS) (72.7% vs. 68.5%, p = 0.441) and leukaemia-free survival rates (62.8% vs. 56.1%, p = 0.383) compared to allo-HSCT for patients with negative MRD, while the advantage of lower non-relapse mortality (1.5% vs. 25.1%, p < 0.001) was offset by a higher cumulative incidence of relapse (CIR) rates (35.7% vs. 18.9%, p = 0.018), especially in high-risk patients. For patients at high risk and with positive MRD, there was a lower trend of 3-year OS (50.0% vs. 66.0%, p = 0.078) and significantly higher CIR rates (71.4% vs. 39.1%, p = 0.018) in auto-HSCT. However, no significant interaction was observed in the tests. In conclusion, auto-HSCT appears to be an attractive treatment for patients with negative MRD after three chemotherapy cycles. For MRD-positive patients, allo-HSCT may be a more effective treatment.

Expert Recommendations for the Diagnosis, Treatment, and Management of Adult B-Cell Acute Lymphoblastic Leukemia in Latin America

PURPOSE

Despite strong induction chemotherapy response rates, only 30%-40% of patients with adult B-cell acute lymphoblastic leukemia (ALL) attain long-term remission. This study analyzes ALL in Latin America (LA) and recommends diagnosis, treatment, and management protocols.

METHODS

The Americas Health Foundation organized a panel of hematologists from Argentina, Brazil, Chile, Colombia, and Mexico to examine ALL diagnosis and therapy and produce recommendations.

RESULTS

Lack of regional data, unequal access to diagnosis and therapy, inadequate treatment response, and uneven health care distribution complicate adult ALL management. The panel recommended diagnosis, first-line and refractory treatment, and post-transplantation maintenance. Targeted treatments, including rituximab, blinatumomab, and inotuzumab ozogamicin, are becoming available in LA and must be equitably accessed.

CONCLUSION

This review adapts global information on treating ALL to LA. Governments, the medical community, society, academia, industry, and patient advocates must work together to improve policies.

Prophylactic or preemptive tyrosine kinase inhibitor therapy after allogeneic hematopoietic cell transplantation for Philadelphia chromosome-positive acute lymphoblastic leukemia

Prevention of disease relapse after allogeneic hematopoietic cell transplantation (allo-HCT) in patients with Philadelphia chromosome-positive acute lymphoblastic leukemia remains a major concern. Maintenance therapy with tyrosine kinase inhibitors (TKIs) after allo-HCT has been used to reduce the incidence of relapse. Two main strategies are employed for using TKIs after allo-HCT: prophylactic TKI therapy, which is given before measurable residual disease (MRD) detection, and preemptive TKI therapy, which is given after MRD detection. These strategies both have advantages and disadvantages in terms of treatment efficacy, adverse events, adherence, and socioeconomic factors. In addition, many issues remain to be resolved because of the lack of large prospective studies on how to use TKIs after allo-HCT. These include indications for prophylactic and preemptive TKI therapy, timing of initiation, frequency of MRD monitoring, TKI selection, dose, and treatment duration. While the current available evidence is extremely limited, this article will discuss these issues after summarizing some representative and recent studies. It will also share a novel indicator that can be used to visualize the reversible transition between molecular relapse and remission by TKI therapy.

Autologous versus allogeneic hematopoietic cell transplantation for older patients with acute lymphoblastic leukemia. An analysis from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Allogeneic hematopoietic cell transplantation (allo-HCT) with reduced intensity conditioning (RIC) is an option for elderly patients with acute lymphoblastic leukemia (ALL). We retrospectively compared results of RIC-allo-HCT from either a matched sibling donor (MSD, n = 209) or matched unrelated donor (MUD, n = 209) with autologous (auto, n = 142) HCT for patients aged 55 years or more treated in first complete remission (CR1) between 2000 and 2018. The probabilities of leukemia-free survival (LFS) at 5 years were 34% for RIC-allo-HCT versus 39% for auto-HCT (p = 0.11) while overall survival (OS) rates were 42% versus 45% (p = 0.23), respectively. The incidence of relapse (RI) and non-relapse mortality (NRM) was 41% versus 51% (p = 0.22) and 25% versus 10% (p = 0.001), respectively. In a multivariate model, using auto-HCT as reference, the risk of NRM was increased for MSD-HCT (Hazard ratio [HR] = 2.1, p = 0.02) and MUD-HCT (HR = 3.08, p < 0.001), which for MUD-HCT translated into a decreased chance of LFS (HR = 1.55, p = 0.01) and OS (HR = 1.62, p = 0.008). No significant associations were found with respect to the risk of relapse. We conclude that for patients with ALL in CR1, aged above 55 years, auto-HCT may be considered a transplant option alternative to RIC-allo-HCT, although its value requires verification in prospective trials.

How I treat with maintenance therapy after allogeneic HCT

Disease relapse is the leading cause of failure for patients receiving allogeneic hematopoietic cell transplantation (allo-HCT). Maintenance therapy administered after allo-HCT is a promising strategy to reduce the incidence of relapse and enhance the curative potential of allo-HCT. Research investigations and clinical applications of this approach have greatly increased in recent years, with an expanding number of available therapeutic agents to introduce in the posttransplant setting. However, many questions and challenges remain regarding the feasibility and clinical impact of maintenance. In this article, we present four common case scenarios addressing select available therapeutic agents as a framework to review published data and ongoing studies and describe our current standard practice in the rapidly evolving field of maintenance therapy after allo-HCT.

Tyrosine Kinase Inhibitor-associated Cerebral Arterial Occlusive Disease Treated with High-flow Bypass Surgery: A Case Report

Nilotinib, one of the tyrosine kinase inhibitors, has been used to treat chronic myeloid leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL). Nilotinib-associated cerebral arterial occlusive disease, which is treated with medicine with/without bypass surgery or stenting, has been sporadically reported to occur. The mechanism of the nilotinib-associated cerebral disease has not been clarified and is still controversial. Here we present the case of a 39-year-old woman with Ph+ ALL treated with nilotinib, which led to symptomatic intracranial arterial stenosis. We performed high-flow bypass surgery and observed the arterial stenotic change in the stenotic portion intraoperatively, whose findings strongly supported the theory of atherosclerosis and seemed to be irreversible.

Real world outcomes in patients with Philadelphia chromosome positive acute lymphoblastic leukemia undergoing allogeneic stem cell transplantation-A single institution experience

Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL) has been associated with a worse prognosis compared to Ph negative ALL. Tyrosine kinase inhibitor (TKI) therapy has led to an improvement in response rates and survival, thus becoming a critical component of therapy. We performed a retrospective cohort study of Ph+ ALL patients treated at the University of Michigan who received TKI therapy pre- and post-allogeneic hematopoietic stem cell transplant (HSCT) from April 2007 to November 2019. The study included 40 patients with Ph+ ALL (47.5% female) with a median age of 54 (24-69) years. Median event-free survival (EFS) was not reached, with a 5-year EFS of 61%. Median overall survival (OS) was not reached, with a 5-year OS of 71%. There was no difference in 2-year EFS or OS for patients on pre-transplant imatinib or dasatinib (p = 0.16, 0.09, respectively), though definitive conclusions are challenging as post-transplant TKI therapy was variable. The incidence of any grade acute graft-versus-host disease (GVHD) was 62.5% (25/40) and any grade chronic GVHD was 77.5% (31/40). Complete molecular remission (CMR) was achieved in 57.5% of patients pre-transplant with no significant difference when stratified by induction TKI (p = 1). Achievement of CMR pre-HSCT showed a trend towards improved 2-year EFS (p=0.0198) but did not significantly change 2-year OS (p = 1). Patients receiving 1^st and 2^nd generation TKIs pre- and post-HSCT seem to have favorable outcomes, although type of TKI (pre-HSCT) did not significantly impact EFS or OS. In addition, attaining a CMR pre-transplant improved EFS, but did not change OS.

Modern Management Options for Ph+ ALL

Simple Summary

The use of tyrosine kinase inhibitors has represented a major step forward in the therapy of Philadelphia chromosome positive acute lymphoblastic leukemia. Recent improvements in the therapy are focused on early use of third generation tyrosine kinase inhibitors, their combination with immunotherapy, the refined indication of allogeneic hematopoietic stem cell transplantation, the optimal use and duration of maintenance therapy, and the management of patients with molecular or hematological relapse with combination of targeted therapies and immunotherapy, including cellular therapies. Improvements in the assessment of measurable residual disease and in the detection of mutations in the ABL1 domain are contributing to the better selection of the therapy for newly diagnosed as well as for relapsed or refractory patients.

Abstract

Impressive advances have been achieved in the management of patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) since the initial concurrent use of imatinib and standard chemotherapy. The attenuation of chemotherapy has proven to be equally effective and less toxic, the use of third generation TKI upfront has improved the frequency of complete molecular response and the survival rate, and the combination of tyrosine kinase inhibitors with immunotherapy has further increased the rate of molecular response to 70–80% after consolidation, which has been translated into a survival rate of 75–90% in recent trials. As a result of these improvements, the role of allogeneic hematopoietic stem cell transplantation is being redefined. The methodology of measurable residual disease assessment and the detection of ABL1 mutations are also improving and will contribute to a more precise selection of the treatment for newly diagnosed and relapsed or refractory (R/R) patients. Finally, new compounds combined with immunotherapeutic approaches, including cellular therapy, are being used as rescue therapy and will hopefully be included in first line therapy in the near future. This article will review and update the modern management of patients with Ph+ ALL.

Safety and outcomes of maintenance therapy with third-generation tyrosine kinase inhibitor after allogeneic hematopoietic cell transplantation in Philadelphia chromosome positive acute lymphoblastic leukemia patients with T315I mutation

Studies using third-generation tyrosine kinase inhibitor (TKI) as maintenance therapy after hematopoietic cell transplantation (HCT) for patients with Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ALL) harboring the T315I mutation remain scarce. We conducted a cohort study to evaluate the safety and outcomes of ponatinib maintenance therapy after HCT in Ph+ALL patients with T315I mutation. BCR-ABL kinase domain mutations were assessed using direct sequencing. Twenty-six Ph+ALL patients with T315I mutation who received allogeneic HCT were enrolled. After HCT, ponatinib was administered as a prophylactic regimen (n = 12) or a preemptive therapy (n = 7). Seven patients did not receive maintenance therapy. Adverse events (AEs) occurred in 69.4 % of patients with ponatinib maintenance, but most presented with mild toxicities. Serious non-hematological AEs were not observed. The 5-year disease-free survival (DFS), overall survival (OS), and cumulative incidence of relapse in patients receiving prophylactic ponatinib were 81.5 %, 91.7 %, and 18.5 %, respectively, whereas they were 39.8 %, 46.0 %, and 48.4 % in the total cohort, respectively. The measurable BCR-ABL transcripts in the first three months after HCT was associated with poor DFS and OS, even with ponatinib therapy. We concluded that maintenance therapy with ponatinib is safe after HCT. Patients with T315I mutation who received prophylactic regimen showed promising results with an acceptable relapse rate and encouraging survival. However, patients with measurable BCR-ABL transcripts early post-transplant had poor outcomes.

The Global Burden of Leukemia and Its Attributable Factors in 204 Countries and Territories: Findings from the Global Burden of Disease 2019 Study and Projections to 2030

Background. Leukemia is a common malignancy that has four main subtypes and is a threat to human health. Understanding the epidemiological status of leukemia and its four main subtypes globally is important for allocating appropriate resources, guiding clinical practice, and furthering scientific research. Methods. Average annual percentage changes (AAPCs) were calculated to estimate the change trends of age-standardized rates (ASRs) from 1990 to 2019 in 204 countries and territories. The risk factors for leukemia death and disability-adjusted life-year (DALY) were also analyzed. In addition, the future trends in ASRs were projected through 2030. Results. The total number of incident cases, deaths, and DALYs from leukemia in 2019 was 0.64, 0.33, and 11.66 million, respectively. Decreasing trends in age-standardized incidence rate (ASIR), the age-standardized death rate (ASDR), and age-standardized DALY rate were detected on a global level while increasing trends in ASIR were detected in the high-sociodemographic index (SDI) regions. The leukemia burden was heavier in males than in females. By cause, acute myeloid leukemia (AML), chronic myeloid leukemia (CML), and chronic lymphocytic leukemia (CLL) were more likely to impose a burden on the elderly, while acute lymphoblastic leukemia (ALL) showed a greater impact in the younger population. A significant positive correlation was observed between SDI and AAPC in ASIR, while SDI was negatively correlated with AAPCs in both ASDR and age-standardized DALY rate. Smoking remained the most significant risk factor associated with leukemia-related death and DALY, especially in males. Similar deaths and DALYs were caused by smoking and high body mass index (BMI) in females. Future projections through 2030 estimated that ASIR and ASDR will continue to increase, while the DALY rate is predicted to decline. Conclusions. Patterns and trends of leukemia burden are correlated with SDI. The estimated contributions to leukemia deaths indicate that timely measures are needed to reduce smoking and obesity.

Treatment of Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia in Adults

Simple Summary

Outcome of patients with Philadelphia-chromosome positive acute lymphoblastic leukemia (Ph+ ALL) dramatically improved during the past 20 years with the advent of tyrosine kinase inhibitors and monoclonal antibodies. Their great efficacy in young and fit patients led to question our reliance on chemotherapy and allogeneic hematopoietic stem cell transplantation. Moreover, these well-tolerated treatments can be safely administrated even in the elderly that represent the majority of Ph+ ALL patient. This review will focus on the recent changes of paradigm in the management of Ph+ ALL patients and the development of novel therapeutic strategies.

Abstract

Philadelphia-chromosome positive acute lymphoblastic leukemia (Ph+ ALL) is the most common subtype of B-ALL in adults and its incidence increases with age. It is characterized by the presence of BCR-ABL oncoprotein that plays a central role in the leukemogenesis of Ph+ ALL. Ph+ ALL patients traditionally had dismal prognosis and long-term survivors were only observed among patients who underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) in first complete remission (CR1). However, feasibility of allo-HSCT is limited in this elderly population. Fortunately, development of increasingly powerful tyrosine kinase inhibitors (TKIs) from the beginning of the 2000′s dramatically improved the prognosis of Ph+ ALL patients with complete response rates above 90%, deep molecular responses and prolonged survival, altogether with good tolerance. TKIs became the keystone of Ph+ ALL management and their great efficacy led to develop reduced-intensity chemotherapy backbones. Subsequent introduction of blinatumomab allowed going further with development of chemo free strategies. This review will focus on these amazing recent advances as well as novel therapeutic strategies in adult Ph+ ALL.

Clinical Value of Measurable Residual Disease in Acute Lymphoblastic Leukemia

Measurable (minimal) residual disease (MRD) status in acute lymphoblastic leukemia (ALL) has largely superseded the importance of traditional risk factors for ALL, such as baseline white blood cell count, cytogenetics, and immunophenotype, and has emerged as the most powerful independent prognostic predictor. The development of sensitive MRD techniques, such as multicolor flow cytometry (MFC), quantitative polymerase chain reaction (PCR), and next-generation sequencing (NGS), may further improve risk stratification and expand its impact in therapy. Additionally, the availability of highly effective agents for MRD eradication, such as blinatumomab, inotuzumab ozogamicin, and chimeric antigen receptor (CAR) T-cell therapies, enabled the development of frontline regimens capable of eradicating MRD early in the treatment course. While long-term follow-up of this approach is lacking, it has the potential to significantly reduce the need for intensive post-remission treatments, including allogeneic bone marrow transplantation, in a significant proportion of patients with ALL.

20-Year Steady Increase in Survival of Adult Patients with Relapsed Philadelphia-Positive Acute Lymphoblastic Leukemia Post Allogeneic Hematopoietic Cell Transplantation

PURPOSE

Relapse after allogeneic hematopoietic cell transplantation (allo-HCT) remains the first cause of transplant failure in patients with Philadelphia-positive (Ph+) acute lymphoblastic leukemia (ALL). In other hematologic malignancies, therapeutic advances resulted in significant improvement over time in survival of patients relapsing after transplant.

EXPERIMENTAL DESIGN

We compared outcomes at European Society for Blood and Marrow Transplantation (EBMT) participating centers of 899 adult patients with Ph+ ALL who relapsed between 2000 and 2019 after allo-HCT performed in first complete remission. Median follow-up for alive patients was 56 months.

RESULTS

Overall, 116 patients relapsed between 2000 and 2004, 225 between 2005 and 2009, 294 between 2010 and 2014, and 264 between 2015 and 2019. Patient and transplant characteristics were similar over the four time periods except for a progressive increase in unrelated donors, peripheral blood stem cells, reduced intensity conditioning, and in vivo T-cell depletion and a progressive decrease in total body irradiation. The 2-year overall survival (OS) after relapse increased from 27.8% for patients relapsing between 2000 and 2004 to 54.8% for 2015 and 2019 (P = 0.001). A second allo-HCT within 2 years after relapse was performed in 13.9% of patients resulting in a 2-year OS of 35.9%. In multivariate analysis, OS from relapse was positively affected by a longer time from transplant to relapse and the year of relapse.

CONCLUSIONS

We observed a major progressive improvement in OS from posttransplant relapse for patients with Ph+ ALL over the years, likely multifactorial including transplant-related factors, posttransplant salvage, and improvement in supportive care. These large-scale real-world data can serve as a benchmark for future studies in this setting. See related commentary by Gale, p. 813.

What Is the Role of HSCT in Philadelphia-Chromosome-Positive and Philadelphia-Chromosome-Like ALL in the Tyrosine Kinase Inhibitor Era?

Previously, the outcome of paediatric Philadelphia-chromosome-positive (Ph+) ALL treated with conventional chemotherapy alone was poor, necessitating the use of haematopoietic stem cell transplantation (HSCT) for the best outcomes. The recent addition of tyrosine kinase inhibitors (TKIs) alongside the chemotherapy regimens for Ph+ ALL has markedly improved outcomes, replacing the need for HSCT for lower risk patients. An additional poor prognosis group of Philadelphia-chromosome-like (Ph-like) ALL has also been identified. This group also can be targeted by TKIs in combination with chemotherapy, but the role of HSCT in this population is not clear. The impact of novel targeted immunotherapies (chimeric antigen receptor T cells and bispecific or drug-conjugated antibodies) has improved the outcome of patients, in combination with chemotherapy, and made the role of HSCT as the optimal curative therapy for Ph+ ALL and Ph-like ALL less clear. The prognosis of patients with Ph+ ALL and persistent minimal residual disease (MRD) at the end of consolidation despite TKI therapy or with additional genetic risk factors remains inferior when HSCT is not used. For such high-risk patients, HSCT using total-body-irradiation-containing conditioning is currently recommended. This review aims to provide an update on the current and future role of HSCT for Ph+ ALL and addresses key questions related to the management of these patients, including the role of HSCT in first complete remission, MRD evaluation and related actions post HSCT, TKI usage post HSCT, and the putative role of HSCT in Ph-like ALL.

How I Use Measurable Residual Disease in the Clinical Management of Adult Acute Lymphoblastic Leukemia

Over the last decade the use of measurable residual disease (MRD) diagnostics in adult acute lymphoblastic leukemia (ALL) has expanded from a limited number of study groups in Europe and the United States to a world-wide application. In this review, we summarize the advantages and drawbacks of the current available techniques used for MRD monitoring. Through the use of three representative case studies, we highlight the advances in the use of MRD in clinical decision-making in the management of ALL in adults. We acknowledge discrepancies in MRD monitoring and treatment between different countries, reflecting differing availability, accessibility and affordability.

Comparison of allogeneic hematopoietic stem cell transplantation and TKI combined with chemotherapy for adult philadelphia chromosome positive acute lymphoblastic leukemia: a systematic review and meta-analysis

OBJECTIVE

This study seeks to clarify whether allogeneic hematopoietic stem cell transplantation (allo-HSCT) is necessary for adult patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) in post-remission based on a comparison with tyrosine kinase inhibitor (TKI) combined with chemotherapy.

METHODS

We searched the Pubmed, Embase, and Web of Science databases and limited the date range for the studies from January 2010 to August 2020. A hazard ratio (HR) with a 95% confidence interval (CI) was employed to assess overall survival (OS) and relapse-free survival (RFS), and an odds ratio (OR) with a 95% CI was used to evaluate the ratio of non-relapsed mortality (NRM) and non-relapsed survival (NRS). All analyses were conducted with Stata software 16.0 and Revman 5.3.

RESULTS

Fifteen studies, totaling 959 patients, were included in our analysis. Among those patients, 473 underwent allo-HSCT, and 486 received TKI plus chemotherapy. The pooled results showed no difference in OS between outcomes for patients receiving TKI plus chemotherapy and those treated with allo-HSCT (HR = 0.76, 95% CI [0.51-1.12], p = 0.16). Patients undergoing allo-HSCT did better than those receiving TKI plus chemotherapy regarding RFS (HR = 0.48, 95% CI [0.37-0.63], p = 0.00), and NRS (OR = 2.64, 95% CI [1.25-5.57], p = 0.00). The NRM rate of the TKI plus chemotherapy group was significantly lower than the allo-HSCT group (OR = 2.33, 95% CI [1.51-3.59], p = 0.00).

CONCLUSION

TKI combined with chemotherapy can be considered a post-remission treatment option for adult Ph+ ALL patients who are ineligible for allo-HSCT. However, more prospective studies with large sample sizes should be carried out in the future.

Dasatinib-based Two-step Induction for Adults with Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia

Dasatinib-based 2-step induction resulted in a 100% CR rate with minimal toxicities and 53% MRD negativity.

This protocol treatment increased the number of HSCTs in CR1, thereby improving 3-year EFS.

The standard treatment for adults with Philadelphia chromosome–positive (Ph⁺) acute lymphoblastic leukemia (ALL) in Japan is imatinib-based chemotherapy followed by allogeneic hematopoietic stem cell transplantation (HSCT). However, ∼40% of patients cannot undergo HSCT in their first complete remission (CR1) because of chemotherapy-related toxicities or relapse before HSCT or older age. In this study, we evaluated dasatinib-based 2-step induction with the primary end point of 3-year event-free survival (EFS). The first induction (IND1) was dasatinib plus prednisolone to achieve CR, and IND2 was dasatinib plus intensive chemotherapy to achieve minimal residual disease (MRD) negativity. For patients who achieved CR and had an appropriate donor, HSCT during a consolidation phase later than the first consolidation, which included high-dose methotrexate, was recommended. Patients with pretransplantation MRD positivity were assigned to receive prophylactic dasatinib after HSCT. All 78 eligible patients achieved CR or incomplete CR after IND1, and 52.6% achieved MRD negativity after IND2. Nonrelapse mortality (NRM) was not reported. T315I mutation was detected in all 4 hematological relapses before HSCT. Fifty-eight patients (74.4%) underwent HSCT in CR1, and 44 (75.9%) had negative pretransplantation MRD. At a median follow-up of 4.0 years, 3-year EFS and overall survival were 66.2% (95% confidence interval [CI], 54.4-75.5) and 80.5% (95% CI, 69.7-87.7), respectively. The cumulative incidence of relapse and NRM at 3 years from enrollment were 26.1% and 7.8%, respectively. Dasatinib-based 2-step induction was demonstrated to improve 3-year EFS in Ph⁺ ALL. This study was registered in the UMIN Clinical Trial Registry as #UMIN000012173.

A case series of patients treated with inotuzumab ozogamicin for acute lymphoblastic leukemia relapsed after allogeneic hematopoietic cell transplantation

This single-center retrospective study was performed in consecutive patients with acute lymphoblastic leukemia who relapsed after allogeneic hematopoietic cell transplantation (HCT) and received salvage therapy using inotuzumab ozogamicin (InO). Ten patients (median age: 27 years) treated between June 2018 and July 2020 who met the eligibility criteria were included in this study. Nine patients received InO in one cycle and seven of these patients achieved complete hematological remission after salvage chemotherapy including InO. Negative minimal residual disease was confirmed in all four evaluable patients. Eight patients were successfully bridged to the subsequent HCT. After HCT, veno-occlusive disease (VOD) developed in three patients, and caused the death of one. No patient received maintenance therapy. At present, five patients are disease-free and alive, and the overall and progression-free survival rates at 1 year were 60% and 40%, respectively. High rates of disease remission and bridging to HCT with comprehensive treatments including InO may have contributed to favorable outcomes. However, further investigation is needed to reduce post-HCT complications including VOD.

Newly proposed threshold and validation of white blood cell count at diagnosis for Philadelphia chromosome-positive acute lymphoblastic leukemia: risk assessment of relapse in patients with negative minimal residual disease at transplantation-a report from the Adult Acute Lymphoblastic Leukemia Working Group of the JSTCT

White blood cell count (WBC) at diagnosis is the conventional prognostic factor in Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph⁺ ALL). Nevertheless, little is known about the impact of WBC at diagnosis considering the minimal residual disease (MRD) status at allogeneic hematopoietic cell transplantation (HCT). We evaluated adult patients with Ph⁺ ALL who achieved negative-MRD and received HCT in first complete remission between 2006 and 2018. The entire cohort was temporally divided into derivation (n = 258) and validation cohorts (n  =  366). Using a threshold of 15,000/μL, which was determined by a receiver operating characteristic curve analysis in the derivation cohort, high WBC was associated with an increased risk of hematological relapse in both the derivation cohort (25.3% vs. 11.6% at 7 years, P = 0.004) and the validation cohort (16.2% vs. 8.5% at 3 years, P = 0.025). In multivariate analyses, high WBC was a strong predictor of hematological relapse in the derivation cohort (HR, 2.52, 95%CI 1.32-4.80, P = 0.005) and in the validation cohort (HR, 2.32, 95%CI, 1.18-4.55; P = 0.015). In conclusion, WBC at diagnosis with a new threshold of 15,000/μL should contribute to better risk stratification in patients with negative-MRD at HCT.

Novel Indicators of Transplant Outcomes for PhALL: Current Molecular-Relapse-Free Survival

Molecular relapse after allogeneic hematopoietic cell transplantation (allo-HCT) has been thought to predict clinical relapse in patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (PhALL). Tyrosine kinase inhibitor (TKI) administration after allo-HCT may dynamically change the status from molecular relapse to molecular remission, but these state changes cannot be accurately represented by conventional survival indicators such as relapse-free survival, where events are usually considered irreversible. We aimed to develop novel indicators of transplant outcomes for allo-HCT recipients with PhALL and to visualize current molecular-relapse-free survival (CMRFS) and current on-TKI status (CTKI), treating molecular relapse or TKI administration after allo-HCT as a reversible event. We retrospectively analyzed 286 patients with PhALL who received allo-HCT between 2000 and 2016 in order to develop the indicators. CMRFS was defined as the probability of molecular remission without clinical relapse or death at any time after allo-HCT. Similarly, CTKI was defined as the probability of TKI administration without clinical relapse or death at any time after allo-HCT. The 1- and 5-year CMRFS rates were 67% and 59%, respectively, whereas the 1- and 5-year conventional molecular relapse-free survival rates were 42% and 37%. The 1- and 5-year CTKI rates were 14% and 8%, respectively. In a post hoc analysis focusing on patients who had achieved a molecular complete remission within 6 weeks (n = 201), the 5-year CMRFS rate (71%) was similar to the 5-year conventional molecular relapse-free survival (molRFS) rate (70%) in the non-TKI group. On the other hand, the 5-year CMRFS rate in the TKI group was 61%, whereas the 5-year conventional molRFS rate was only 38%. CMRFS and CTKI might become useful indicators of transplant success in terms of survival, leukemia-free status, and treatment-free status at any time point. Future extension of these survival models to other clinical situations is warranted.

Impact of TKIs post-allogeneic hematopoietic cell transplantation in Philadelphia chromosome-positive ALL

How to best use tyrosine kinase inhibitors (TKIs) of BCR-ABL after allogeneic stem cell transplantation for Philadelphia chromosome–positive acute lymphoblastic leukemia (ALL) is unknown but will almost certainly not be addressed by a definitive randomized trial. Saini and colleagues provide a large body of observational data to reinforce earlier circumstantial evidence favoring prophylactic use of TKIs for at least 2 years posttransplant.

Dasatinib in the Management of Pediatric Patients With Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia

Acute leukemia is the most common cancer in childhood; in particular, acute lymphoblastic leukemia (ALL) represents roughly up to 80% of all cases of acute leukemias in children. Survival of children with ALL has dramatically improved over the last few decades, and is now over 90% (versus 40% of adult patients) in developed countries, except for in infants (i.e., children < 1 year), where no significant improvement was registered. Philadelphia positive ALL (Ph+ALL) accounts for around 3% of cases of childhood ALL, its incidence increasing with patient's age. Before the era of tyrosine-kinase inhibitors (TKIs), pediatric Ph+ALL showed a worse prognosis in comparison to other forms of ALL, and was managed with intensive chemotherapy, followed, whenever possible, by allogenic hematopoietic stem cell transplantation (HSCT) in first morphological complete remission. TKIs have revolutionized the current clinical approach, which involves combinations of imatinib plus standard chemotherapy that can abrogate the negative prognostic impact conferred by the presence of BCR/ABL1 rearrangement, resulting in the probability of event-free survival (EFS) being significantly better than that recorded in the pre-TKI era. Long-term follow-up confirms these data, questioning the role of a real advantage offered by HSCT over intensive chemotherapy plus TKI in all Ph+ALL pediatric patients. Imatinib was the first generation TKI and the prototype of targeted therapy, but over the years second- (dasatinib, nilotinib, bosutinib) and third-generation (ponatinib) TKIs showed a capacity to overcome resistance to imatinib in Ph+ hematological neoplasms. Given the effectiveness of the first-in-class TKI, imatinib, also the second-generation TKI dasatinib was incorporated in the treatment regimens of Ph+ALL. In this manuscript, we will discuss the role of this drug in pediatric Ph+ALL, analyzing the available data published to date.

AML and the art of remission maintenance

Relapse in acute myeloid leukemia (AML) is common, especially in older patients, and there is currently no standard of care maintenance therapy for those who achieve complete remission. Finding effective, tolerable maintenance therapy to prolong remission has been a goal for decades, but early clinical trials testing a variety of agents demonstrated disappointing results with no overall survival benefit. CC-486, an oral hypomethylating agent, was recently approved in the United States for maintenance treatment in patients with AML in first remission following chemotherapy. A number of ongoing studies are assessing various therapeutics in the maintenance setting, including other hypomethylating agents, targeted small-molecule inhibitors, monoclonal antibodies, and immunomodulators. New strategies are needed to identify patients most likely to benefit from maintenance therapy, including those for whom a preemptive approach reliant on monitoring of measurable residual disease would be advantageous.

Development and validation of a disease risk stratification system for patients with haematological malignancies: a retrospective cohort study of the European Society for Blood and Marrow Transplantation registry

BACKGROUND

Diagnosis and remission status at the time of allogeneic haematopoietic stem-cell transplantation (HSCT) are the principal determinants of overall survival following transplantation. We sought to develop a contemporary disease-risk stratification system (DRSS) that accounts for heterogeneous transplantation indications.

METHODS

In this retrospective cohort study we included 55 histology and remission status combinations across haematological malignancies, including acute leukaemia, lymphoma, multiple myeloma, and myeloproliferative and myelodysplastic disorders. A total of 47 265 adult patients (aged ≥18 years) who received an allogeneic HSCT between Jan 1, 2012, and Dec 31, 2016, and were reported to the European Society for Blood and Marrow Transplantation registry were included. We divided EBMT patients into derivation (n=25 534), tuning (n=18 365), and geographical validation (n=3366) cohorts. Disease combinations were ranked in a multivariable Cox regression for overall survival in the derivation cohort, cutoff for risk groups were evaluated for the tuning cohort, and the selected system was tested on the geographical validation cohort. An independent single-centre US cohort of 660 patients transplanted between Jan 1, 2010, and Dec 31, 2015 was used to externally validate the results.

FINDINGS

The DRSS model stratified patients in the derivation cohort (median follow-up was 2·1 years [IQR 1·0-3·2]) into five risk groups with increasing mortality risk: low risk (reference group), intermediate-1 (hazard ratio for overall survival 1·26 [95% CI 1·17-1·36], p<0·0001), intermediate-2 (1·53 [1·42-1·66], p<0·0001), high (2·03 [1·86-2·22], p<0·0001), and very high (2·87 [2·63-3·13], p<0·0001). DRSS levels were also associated with a stepwise increase in risk across the tuning and geographical validation cohort. In the external validation cohort (median follow-up was 5·7 years [IQR 4·5-7·1]), the DRSS scheme separated patients into 4 risk groups associated with increasing risk of mortality: intermediate-2 risk (hazard ratio [HR] 1·34 [95% CI 1·04-1·74], p=0·025), high risk (HR 2·03 [95% CI 1·39-2·95], p=0·00023) and very-high risk (HR 2·26 [95% CI 1·62-3·15], p<0·0001) patients compared with the low risk and intermediate-1 risk group (reference group). Across all cohorts, between 64% and 65% of patients were categorised as having intermediate-risk disease by a previous prognostic system (ie, the disease-risk index [DRI]). The DRSS reclassified these intermediate-risk DRI patients, with 855 (6%) low risk, 7111 (51%) intermediate-1 risk, 5700 (41%) intermediate-2 risk, and 375 (3%) high risk or very high risk of 14 041 patients in a subanalysis combining the tuning and internal geographic validation cohorts. The DRI projected 2-year overall survival was 62·1% (95% CI 61·2-62·9) for these 14 041 patients, while the DRSS reclassified them into finer prognostic groups with overall survival ranging from 45·7% (37·4-54·0; very high risk patients) to 73·1% (70·1-76·2; low risk patients).

INTERPRETATION

The DRSS is a novel risk stratification tool including disease features related to histology, genetic profile, and treatment response. The model should serve as a benchmark for future studies. This system facilitates the interpretation and analysis of studies with heterogeneous cohorts, promoting trial-design with more inclusive populations.

FUNDING

The Varda and Boaz Dotan Research Center for Hemato-Oncology Research, Tel Aviv University.